1. Field of the Invention
The present invention relates to a recording and reproducing unit that performs recording and reproducing on optical disc recording media on which recording/reproducing of information is performed by irradiation of light, specifically, to a recording and reproducing unit that has three or more independent laser beam irradiation systems (recording/reproducing channels) and performs information recording and information reproducing at the same time on the optical disc recording media and a method therefor.
2. Description of the Related Art
Optical disc recording media such as CD (compact disc), DVD (Digital Versatile Disc), and BD (Blu-ray Disc: Registered Trademark), for example, on which recording/reproducing of information is performed by irradiation of light are widely used, and further, recording and reproducing units that perform recording and reproducing on them (optical disc drive units) are widely used.
Here, for example, there is a recording and reproducing unit for optical discs applied to a drive unit for professional-use video camera equipment as disclosed in JP-A-2006-107638 (Patent Document 1).
In the field of the professional-use video camera equipment, it is desired that, during recording of imaged video data in amounted optical disc, an arbitrary part of video data that has already been recorded on the optical disc may be reproduced at the same time.
As one technique for realizing the simultaneous recording and reproducing, a technique disclosed in JP-A-2007-89214 (Patent Document 2) may be cited.
In Patent Document 2, a technology using only one typical optical head (optical head having only one route of laser beam irradiation system that irradiates an optical disc with a laser beam) to perform simultaneous recording and reproducing on an optical disc is disclosed.
As below, one route of laser beam irradiation system is referred to as “one channel (ch)”, and the configuration of performing recording and reproducing using only one typical optical head as described above is referred to as “1-head/1-ch configuration”.